Pumps and intensifiers are devices for introducing energy into a fluid so as to move it from point A to point B or to pressurize it to perform work. The word "pump" generally refers to apparatus that converts shaft power of an engine or motor to kinetic energy in moving fluid or potential energy in pressurized fluids, or both. Intensifiers are devices that transfer stored energy from one pressurized fluid, generally referred to as a working fluid, to another fluid, generally referred to as a system fluid. The two fluids are often different but can be the same.
There are many types of pumps. For instance, pumps are critical to the operation of fluid power systems. The selection of available pumps is very wide when the system pressure is low and the system operation is simple. The selection becomes narrower when the system pressure is very high, and the system operations are more demanding. By way of example, today's waterjetting processes are carried out at very high flow and pressure.
High-pressure waterjetting is now an accepted method for removing deteriorated coatings from various structures, such as storage tanks, bridges, and ship hulls. The system pressure of these processes is commonly 40,000 psi or higher. At these pressures, the fluid induced forces and stresses are very high. Specialized high-pressure pumps are required for handling water at such pressure levels.
Due to the high cost of labor, downtime, and dry dock fees, the cleaning of structures must also be performed at high speed and with good results. Waterjetting must be applied not only at high pressures but also at high flow rates. The flow capacity of these high-pressure pumps must also be very high.
Many waterjetting operations cover a large surface area, such as the hull of today's supertankers. The mobility of the pump system is one concern, because it may have to be moved often. The weight and compactness of the pump are related concerns.
Pumps for today's waterjetting processes must also be versatile and reliable. The high-pressure water flow needs to be turned on and off frequently. This task is simple when the system pressure is very low, but more difficult at very high pressures. Popular crankshaft pumps do not have this capability. The user has to dump the water or to shut off the motor or engine if the high-pressure waterjet is to be temporarily shut off.
The reliability of the pump is also important in today's waterjetting processes. The down time must be kept at a minimum, otherwise the profit of an operation can be lost.
Current waterjetting processes are often carried out with crankshaft pumps, also known as "oil field" pumps. These pumps are large and bulky, and typically have 3 or 5 pistons linked mechanically to a crankshaft. If one piston fails, the entire pump is basically out of order. If the crankshaft develops faults, the pump also fails. These pumps have no mechanism for stoppage. The only way to stop output is to dump the flow or shut off the engine or motor.
At present, crankshaft pumps are limited to a maximum system pressure of 40,000 psi. For operations at pressures above 40,000 psi, double-acting fluid pressure intensifiers are used. These hydraulically powered intensifiers have two opposed plungers sharing a common power piston. The output power of these intensifiers is discontinuous, and dead-volume high-pressure accumulators are required to reduce the pressure pulsations. These intensifiers are also very bulky in respect to their flow capabilities and have a geometry not conducive for many applications. The intensifiers also require electricity to operate, which can be difficult to provide in remote waterjetting operations.